Rimfire Wildcats

Four or five years age I got these two Rimfires at the St Louis Show. I purchased them from a German gentleman. Dispite the US headstamps he said they were of German origin. I don’t remember for sure but I think he said they were Police experimentals.

The first is a 5mm Remington Rimfire Magnum necked down to 17 caliber.

It has an impress “U” headstamp
Case length: 1.013" (25.72mm)
Bullet Dia: .1710" (4.36mm)
Neck Dia:.1895" (4.36mm)
Total weight: 50.88 grains (3.297 grams)
Total Lenght: 1.418" (36.00mm)
The bullet is a jacketed hollow point.

The second is based on a 22 rimfire Magnum Case.

At first I thought it was .17 cal but the bullet diameter is .1755 (4.45mm)
all the 17 cal rimfires and wildcats I known of have .1710 diameter bullets. Could it be a 4.5mm wildcat? It has a Wincherster “Super-X” headstamp.

Case length: 1.063" (26.97mm)
Bullet Dia: .1755" (4.45mm)
Neck diameter: .1960" (4.95mm)
Total Length:1.3855" (35.19mm)
Total weight: 46.48 grains (3.0123 Grams)

The bullet is a pointed full metal jacket. It has an unusual flat squared off tip and a deep groove at the case mouth crimp.

Any information on either of these would be much appreciated.




Can’t say that I know what either one is. I have a small collection of the sub-calibers but they’re not one of my big interests.

There was a rimfire craze a few years ago where guys were getting unfired rimfire cases and necking them down to all of the smaller calibers. All of them preceded the current crop of factory cartridges.

I suppose the 5mm Remington necked to .17 could have been one of them.

There is a 17 cal version of your second cartridge called the 17 Vixen.

If you go to the following site you may find what you’re looking for. Or you could post the Q over there.

Good Luck



Ray, thanks for the responce. That’s an interesting web site. There was a good interview there with Bill Eichelberger, one of the kings of small caliber wildcats. I’m going to post my questions there maybe I’ll get a responce.

I thought the necked down 22 Mag might be a Vixen but all the info on the Vixen I can find says it has a 0.171 bullet and the neck looks longer than the .17 I have.

Wildcats aren’t my thing, to hard to ID! Too many people making too many odd cartridges!